Denon Protection Mode Question

Hi Tech48,

I was really happy to come across this site and your reply to the Denon AVR post about the protecion mode. You sound like the only guy that really knows whats going on. You said generaly the problem is one of 3 things and I checked the other two but what about this one?

Problem 1. This is the most common problem. One of the front channels shorts out. On the big heat sink the front channels are at each end. It is the front left channel (close to the display) This requires that the output transistors be replaced as well as some driver transistors and some resistors and a capacitor. Lots of work for a blown channel. Denon has put out a bullitin to upgrade the bias transistor and change a couple of resistors to help compensate for this failure. That channel overheats more than any other channel.

Is there any chance you can get more specific on this repair? I have the service manual and schematics and I am a technicin in training. I recently started working in a electronics lab and this is a little project I'm taking on.
Any expertise would really be appreceiated. A guy gave me this receiver and said I could keep it if I got it going. Its a AVR-1907. he said a power surge hit his house and it didn't work afterwards.

Hi, tech48... I appreciate you sharing your knowledge... Can I ask youa question... I have a common Denon problem -- no audio anymore... Ihave a 3-yr old Denon AVR-2106, no audio anymore after ahutting downone day and a single pop from all speakers came... Turns on, startsnormally, flashing then steady green, ending in 'Receiver' display, no"Protected Mode' display, I hear very slight power relay click-on (nota pop), just no audio... What do you suggest. is transformer bad?thermal fuse blown? I have some electronics repair skills. Thanks...

Hi, tech48... I appreciate you sharing your knowledge... Can I ask you
a question... I have a common Denon problem -- no audio anymore... I
have a 3-yr old Denon AVR-2106, no audio anymore after ahutting down
one day and a single pop from all speakers came... Turns on, starts
normally, flashing then steady green, ending in 'Receiver' display, no
"Protected Mode' display, I hear very slight power relay click-on (not
a pop), just no audio... What do you suggest. is transformer bad?
thermal fuse blown? I have some electronics repair skills. Thanks...

I will be happy to help you figure this one out. First, let's make sure that the output channel is blown. Have you checked the output transistors on the heat sink? Are they shorted? This is the first thing to check for this failure. If you have verified that the channel is in fact bad, I will then give you a list of all the parts you need to replace.

You mentioned that the unit took a power surge. If this is true, it may not have a shorted channel, it could be the power transformer that is bad.

Does the unit turn on and then go into the protect mode with the display lighting up and then it shuts down a few seconds later?

Have you checked the fuse that is right near where the power cord plugs into the main board?

I just want to confirm the actual problem before proceeding any further, it will save both you and I time and trouble. Please wait to rate this solution until we have finished our communications and are sure of the problem.

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Hi,
This is because your unit goes in to protection mode because of some bad connection in the input/output section .Disconnect your spkrs,inputs..turn the volume is Down all the way and power it up,Check your wiring for shorts at the inputs and outputs.
at your service
sreejith

This is a protection mode. The receiver protection circuit detects an internal problem like missing power supply voltage or blown channel and shuts down the receiver. You need to bring the unit to a repair facility.

It sounds like there is a problem with the differential circuit. The bias I am not sure about, as every unit is different. You should get the service manual to be sure or call Denon and see if they can give you an idea. Good Luck